1. Field of the Invention
The present invention generally relates to a metal/ceramic bonding substrate and a method for producing the same. More specifically, the invention relates to a metal/ceramic bonding substrate wherein a circuit forming metal plate is bonded to one side of a ceramic substrate and a radiating metal base plate is bonded to the other side thereof, and a method for producing the same.
2. Description of the Prior Art
In recent years, as an insulating substrate for a power module for controlling heavy-current for electric vehicles, electric railcars, machine tools and so forth, there is used a metal/ceramic bonding substrate wherein a metal circuit plate is bonded to a ceramic substrate and a flat-plate-shaped radiating metal base plate is bonded to the other side thereof (see, e.g., Japanese Patent Laid-Open No. 2002-76551).
However, in order to increase the insulation distance of conventional metal/ceramic bonding substrates to improve reliability on insulation thereof, it is required to increase the distance between a metal circuit plate and a metal base plate, so that it is required to increase the size of the metal/ceramic bonding substrate. In addition, the reliability of conventional metal/ceramic bonding substrates to heat cycles is not always sufficient.